One of the major problems facing the agriculture industry is the control of insect pests and disease. Of the many diseases which affect plants, a great number are of bacterial or fungal origin. Fungal and bacterial plant diseases can be especially problematic in hot, humid climates such as that which exists in Florida and other southern areas.
An example of an important vegetable disease caused by bacterial is bacterial leaf spot caused by Xanthomonas campestris pv vesicatoria. This pathogen causes widespread disease affecting Florida tomatoes (Pohronezny, K., V. H. Waddill, D. J. Schuster, and R. M. Sonoda [1986] Plant Dis. 70:96-102). Yield losses of up to 30% due to bacterial leaf spot have been reported (Pohronezny, K., and R. B. Volin [1983] HortScience 18:69-70).
Control efforts to date have focused on the identification of chemical control agents. At the present time, registered commercial pesticide sprays do not provide an acceptable level of control of bacterial leaf spot. A combination of copper and mancozeb provides a limited amount of control, but it is primarily effective only at low disease pressure.
In addition to being largely ineffective, current efforts to control fungi and bacteria present the further disadvantages of polluting the environment and creating potential health hazards to agricultural workers and to consumers, who may be exposed directly to the chemicals during application or to residues which can remain on the crops. Additional problems associated with traditional chemical pesticides include the development of resistance in target species, detrimental effects of these chemicals on non-target species, and phytotoxic reactions by treated plants.
Because of the problems associated with the use of traditional fungicides and bactericides, safer and more effective methods of control for bacterial and fungi are clearly needed. This is true, not only for use on tomato crops, but also for other crop plants and for non-agricultural uses as well.